This invention relates to a method and apparatus for recording surface topology on recording films like those disclosed in said applications, the very sensitive continuous tone type of films disclosed in U.S. Pat. No. 4,082,061 and application Ser. No. 827,490 being the films best suited for use in the present invention. The method and apparatus of the invention has its most important present utility in providing excellent quality fingerprints, and records of skin and other tissue surface topology useful in medical diagnosis and research, and for educational purposes where, for example, it is desired to project plant and animal tissue surfaces on a projection screen in a classroom. It also provides surface topology of metals and other materials to detect micro-sized cracks and other surface defects.
The initial surface topology record produced by the invention is a full-sized film transparency record useful immediately as is, or which can be readily projected in magnified form, if desired, onto a screen or photographic film, where almost microscopic details of tissue surface topology become readily visible.
Heretofore, the recording of fingerprints has generally been obtained by coating the fingers with ink and then transferring the ink-formed image onto a piece of paper. This is a very messy and inconvenient method of recording fingerprints, and most sophisticated methods and apparatus for recording fingerprints without the use of ink, such as by photographic means, have not heretofore been developed which are sufficiently easy to carry out or use to be feasible for use in police stations and the like.
Other techniques have been provided for recording the surface topology of skin and other tissue. Some of these methods generally involve taking microscopic pictures of tissue severed from the human body. In such case, recorded images are generally formed on high-resolution silver halide film, requiring a time-consuming developing process which does not make the skin topology involved immediately available to the doctor or researcher. These methods are convenient for obtaining the tissue topology of live skin, since it is not feasible to place the particular area of the body involved into the field of a microscope where, to take effective pictures, the skin involved must be pressed against a flat surface to obtain perfectly focused images of the entire skin area involved, while projecting light upon the skin area involved which is necessary to expose the film.
U.S. Pat. No. 3,533,823 to W. H. Newkirk et al discloses a method of making a fingerprint when a finger is pressed upon an imaging material coated on a metal substrate heated to a temperature substantially above room temperature but sufficiently low as not to burn the users fingers. The imaging material is one which has a hysteresis characteristic where the film initially has a very low reflectivity (i.e. black) at room temperature. When elevated above room temperature it progressively becomes more reflective (e.g. approaching a pure red color). The imaging layer has a given degree of reflectivity prior to the application of a finger thereto. When a finger is placed upon the imaging layer, the points thereof contacted by the ridges of the finger cool the same so that these portions of the imaging layer will have a different degree of reflectivity. When the finger is removed from the imaging layer, the portions thereof previously cooled are heated to the same temperature as the rest of the same. However, because of the hysteresis effect of the imaging layer the degree of reflectivity of the previously cooled portions of the imaging layer will be different from those not originally contacted by the ridges of the finger. The pattern of the ridges of the user's finger will, therefore, be present on the imaging layer until the temperature of the imaging layer is lowered to room temperature where all color differentiation therein disappears. A photograph of the original imprint must thus be taken to obtain a permanent record of the fingerprint. The requirement of a camera as part of the process of providing a permanent record of a fingerprint makes the process involved a very unwieldly one. The only advantage of this process over fingerprinting process utilized prior thereto is that it avoids the necessity of using messy fingerprint ink.
U.S. Pat. No. 3,070,428 to Cohen discloses a process for reproducing negative images of the raised portion of metal surfaces applied to the imaging layers of Thermofax papers or transparencies which must be bulk-heated to substantially elevated temperatures as disclosed in this patent. These temperatures fall in the range of from about 50.degree. to 250.degree. C. and the heat is applied for as short a period as 0.1 seconds and for as long as 60 seconds. The specific examples given in the patent specify 5 or more seconds of heat application to achieve the desired results. The areas of the Thermofax paper engaged by the raised portions of a metal surface are cooled thereby, so that these portions thereof are not affected by the heat, whereas those portions thereof not contacted by the metal surface are heat-imaged to a dark color, black in the example given in the patent.
The process for reproducing negative images of metal surfaces disclosed in this Cohen patent are manifestly not suitable for making fingerprints. Thus, the necessity for bulk heating the substrate of the papers requires heat application times to raise the temperature of the paper to the high imaging temperatures that would cause at least a risk of serious discomfort and probably would cause a serious risk of burning a user's finger should the process disclosed be used to obtain fingerprints. One reading this patent would not, therefore, think of applying the process thereof to obtaining fingerprints.
One further serious disadvantage of utilizing Thermofax papers and transparencies to provide an image of even a metal surface topology is that the images produced are damaged or destroyed by heat and readily deteriorate. Therefore, such papers do not have the desired archival properties for many applications like fingerprint records for police files.
It is, accordingly, an object of the invention to provide a process and apparatus for recording details of surface topology of various surfaces, including live skin and other tissues, which do not require camera equipment or the application of any ink or other imaging materials to the surface involved. Another object of the invention is to provide a method and apparatus as described wherein the application of the surface to be recorded to a recording film produces an immediate image, preferably an image transparency, which can be readily projected by conventional transparency projection equipment.
A further object of the invention is to provide a method and apparatus as just described which does not require the external heating of the imaging film involved, so that no problems of burning or discomfort to live skin tissue is possible.
A still further object of the invention is to provide a method and apparatus as described which produces a record of said surface topologies immediately upon exposure of the recording medium to radiant energy, like an Xenon flash unit or the like, and without using any chemicals or other consumable materials.
Another object of the invention is to provide a method and apparatus as described which produces a permanent image having such archival properties that no special temperature or humidity conditions are required for the storage thereof.
Still another object of the invention is to provide a method and apparatus as described which has such a high degree of resolution that details which are clearly recorded are as small as about 3-5 micron in size.
A further object of the invention is to provide a method and apparatus as described where unskilled personnel can be used to practice the method or operate the apparatus thereof.